A retired British couple who are facing extradition to the US are being held at Heathrow Police Station and will now be flown out of the UK today, it is understood.

Grandparents Paul and Sandra Dunham were taken to hospital last Thursday after they took a drug overdose in an apparent suicide bid the night before they were due to hand themselves in to police and in turn to US marshals.

The couple, both 58, were remanded in custody at Westminster Magistrates Court on Friday after Senior District Judge Howard Riddle concluded they had taken the drugs deliberately to avoid or delay their extradition to face fraud charges.

Kaim Todner solicitors confirmed the couple are set to be extradited to Maryland. It had been expected that the Dunhams would be flown to the US today, but a source familiar with the situation has said they are being held at Heathrow Police Station overnight before being extradited today.

The couple's solicitor Karen Todner said: "Mr and Mrs Dunham are a hard-working couple from Northamptonshire who strenuously deny the allegations against them. Nevertheless this country is forcibly sending them to America to face trial in a justice system where plea arrangements are effectively forced upon people.

"I understand David Cameron has recently stated that the Abu Hamza conviction shows that we ought to be extraditing people to America with greater expedition. What in fact this case shows is that Mr Abu Hamza should have stood trial in the United Kingdom and faced British justice.

"How many people like Mr and Mrs Dunham have to be extradited before this Government will uphold the promises they made whilst in opposition to change this treaty with America?"

The couple lost a High Court battle last month against extradition to stand trial over fraud charges relating to Mr Dunham's company, Pace.

Mr Dunham, who was chief executive, president and a 20% shareholder in the US company which manufactured soldering irons for the electronics industry, was indicted on 13 counts of fraud and money laundering by a grand jury in Greenbelt, Maryland, in December 2011.

Mrs Dunham is accused of eight counts of fraud for allegedly aiding and abetting him. The couple deny any wrongdoing.

Journalists due to take a statement outside the Dunhams' property in Northampton last Thursday alerted police when the couple did not answer the door.

Officers forced the door open and contacted paramedics, who arrived in two ambulances and took the couple to Northampton General Hospital, where they spent the night.

Asked if enough consideration had been given to the Dunhams' mental health, Home Secretary Theresa May said: "The law now is that the Home Office, the Home Secretary, does not have the power to intervene.

"These are matters that go before the court and it's obviously for their legal representatives to decide whether they wish to take matters further before the court.

"But the decisions about the extradition are now for the court and not for the Home Secretary to take."